Sources : Paradisi

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Birds 5.17): The birds of paradise [aves paradisi] are so commonly called, not because they are from paradise, but because of their remarkable beauty. For they are of such beauty and glory, that it is believed that they lack no color. They are the size of a goose, with a voice so sweet and pious, that it can arouse devotion and joy in a man. But if it is ever captured and taken away, it moans and does not stop crying until it is restored to freedom. It lives happily on the banks of the Nile and is rarely found elsewhere. There are also other birds in the same parts, called birds of paradise, because it is not known whence they come or whither they go. For they do not seem to come together, but at certain times they collectively leave the lands which they temporarily inhabit, and thus retire. Their color is brown and small, and their size is smaller than coins. - [Badke translation/paraphrase]